Robots are, at a very rapid pace, becoming increasingly more important in todays technology as responsive tools performing programmed functions. However, robots are not particularly sensitive to the environments in which they perform. For example, the ability of robots, in their present state of development, to touch and sense an object or a force and report back with reliability, the location, magnitude and direction of the force application of what it has touched, does not exist. This problem has received considerable attention, resulting in touch sensors being developed for robotics as well as many other purposes, but to date they have not been particularly successful.
One of the objects of this invention is to produce a reliable touch sensor device suitable for use in a robot and which would meet the criteria of being able to determine location, magnitude and direction of a force it comes in contact with.
Another object of this invention is to produce a touch sensing device meeting the above criteria and which has the versatility for utilization not only in robotics but outside that field as well. For example, such devices have great potential as touch sensitive mechanics for computers and calculators, inter alia.
Position and force indicating systems are not new. Many involve echo signals, light beam interruptions, capacitance change, wire contact etc. As pointed out in prior art patents directed to this area, among the different position and or force indicating systems known heretofore, those which operate by the application of pressure applied to a point, the location and magnitude of which is to be determined, generally require a great number of pressure sensors fixedly secured to the surface where the position of the point is to be determined. Generally, the sensors positions correspond to predetermined points on said surface. The number of possible positions which can effectively be determined is then limited to the number of sensors the surface is able to carry.
Some of the systems referred to employed conductive wafers sandwiched between two layers of parallel wires laid at right angles to each other to form a N.times.N matrix of points which produced N.sup.2 outputs. To achieve acceptable accuracy over an area as small as a four inch square, thousands of outputs were necessary.
The invention disclosed U.S. Pat. No. 3,657,475 to Peronneau addressed the problem of the excessive numbers of outputs by developing a position indicating system for determining the coordinates of a point on a two dimensional surface to which static force is applied. It comprised a rigid plate fixed to the surface by means of at least three spaced apart sensors. Each sensor delivered an output signal which was proportional to its distance from the point of application of the force. The signals were then processed in an electronic unit generating two voltages which represented the coordinates of the point of application of the force to the surface, as measured with reference to two axes determined by the three sensors.
While the Peronneau invention has been generally considered a pioneer in its field, it was limited by the fact that the input force had to be static and it measured only the coordinates of the point of force on a two dimensional surface and not the magnitude of the force but still was limited to a two dimensional surface.
The invention disclosed in U.S. Pat. No. 4,121,049 to Roeber addressed this problem and resulted in a system which measured both location and magnitude of the force. Roeber employed three spaced sensors, each of which delivered an output signal proportional to both the applied force and the coordinates of the force. The signals were fed into a processor which computed the force and its coordinates.
The present invention addresses itself to not only simultaneously determining the coordinates of a force and its magnitude, but its direction as well on a three dimensional surface.